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October 27

Can sterile neutrinos (if exist) decay, if there don't really exist virtual particles?

The background of my question is the following two facts:

Our artricle sterile neutrino states: The production and decay of sterile neutrinos could happen through the mixing with virtual ("off mass shell") neutrinos.

While our article Virtual particles states: they are by no means a necessary feature of QFT, but rather are mathematical conveniences — as demonstrated by lattice field theory, which avoids using the concept altogether.

HOTmag (talk) 06:34, 27 October 2024 (UTC)[reply]

The statement that "x could happen if y" does not in itself exclude the possibilities that (absent y) x could also happen if z, or w, etc. Frankly, this is all so deep in the Jungles of Conjecture (that vast expanse beyond the Mountains of Hypotheses) that definitive answers probably don't yet exist, and Nobel prizes will probably be given for finding answers to such questions. Or so I think: perhaps some post-doctoral particle physicist will correct me. {The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 12:53, 27 October 2024 (UTC)[reply]

As for your first sentence: Of course. I didn't think otherwise. HOTmag (talk) 13:04, 27 October 2024 (UTC)[reply]

Does anything "really" exist? If we answer yes, what does it mean to "really" exist? We have models that make observable predictions. We say that atoms exist because the predictions of the atomic model were actually observed. One observable prediction of virtual particles is the Casimir effect, which was experimentally observed. They lack the stability of other particles, just like the waves that make the surf have no long-time stability. It may be possible to develop a form of hydrodynamic theory that accurately describes the observable effects of surf without introducing the concept of a wave. Does this then mean these waves do not "really" exist? --Lambiam 16:45, 27 October 2024 (UTC)[reply]

Are you responding to me, or (also?) to the quote I quoted from our article virtual particle? HOTmag (talk) 18:40, 27 October 2024 (UTC)[reply]

I am mainly responding to the question as formulated in the heading of this thread. The question is unanswerable if the meaning of "really exist" is not clear (which it isn't). --Lambiam 05:26, 28 October 2024 (UTC)[reply]

Let's put it this way: Do you agree to the content of the second quote under the header? IMO, it actually says that there don't necessarily exist virtual particles. This is what I meant by "don't really exist". But if you think it says something else, you're invited to tell what you think it says.

(Re. Casimir effect, its article in Wikipedia states: Although the Casimir effect can be expressed in terms of virtual particles interacting with the objects, it is best described and more easily calculated in terms of the zero-point energy of a quantized field in the intervening space between the objects).

HOTmag (talk) 06:32, 28 October 2024 (UTC)[reply]

I think it is theoretically possible to develop QCD and QFT to such an extent that it successfully describes macroscopically observable events without introducing the concept of particle. However, this theory would be extremely unwieldy and in practice mathematically untractable – and therefore pretty useless. Particles are a mathematical convenience, but a convenience we cannot do without. It may be possible that some practical version of QFT avoids the concept of virtual particle, but lattice field theory is not an alternative to QFT but a collection of mathematical approaches for obtaining QFT predictions by computer simulation. It is itself a mathematical convenience. Therefore, in my opinion, the sentence relegating virtual particles to a status of mere mathematical conveniences is not so much false as misleading. --Lambiam 19:28, 28 October 2024 (UTC)[reply]

Resolved

According to this video: "It's an easier transition from sterile neutrino to electron-neutrino".

So indeed, perhaps a sterile neutrino doesn't decay (as reqiured in the header), but still, it can (apparently) oscillate - becoming an electron neutrino. HOTmag (talk) 12:07, 28 October 2024 (UTC)[reply]

Global deforestation runoff

What is the global deforestation runoff in km3, which is part of the 40k km3 of global runoff* in general?

Trenberth KE, Smith L, Qian T, Dai A, Fasulo J (2007). Estimates of Global Water Budget and Its Annual Cycle Using Observational and Model Data. Journal of Hydrometeorolgy 8(4):758-769. DOI: org/10.1175/JHM600.1.

Fred weiers (talk) 07:44, 27 October 2024 (UTC)[reply]

Please consult this article: "Deforestation-induced runoff changes dominated by forest-climate feedbacks". My layperson's summary: it's complicated. --Lambiam 16:20, 27 October 2024 (UTC)[reply]

Is Big Bang nucleosynthesis backwards?

The article says the universe started with electrons and protons then created neutrons through nucleosynthesis, but whataboutism those places in the current universe that are too dense for electrons to exist? Shouldn't the universe have started out with all sorts of exotic particles filling in every possible energy state that then phase changes to neutronium as soon as the density is low enough? The neutrons aren't bound together by the Strong Force and hence thermally scatter as the density drops to decay completely away over the next hour, with Lithium and Helium being the result of neutron capture, not fusion? Hcobb (talk) 14:01, 27 October 2024 (UTC)[reply]

In nucleosynthesis, including the Big Bang nucleosynthesis, neutrons and protons combine to form nuclei. In electron capture, a proton of a nucleus turns into a neutron. For example, a nickel nucleus with 28 protons may turn into a cobalt nucleus with 27 protons. In a sufficiently hot environment, nothing is stable; all reactions may go either way, as they certainly did in the first few seconds after the Big Bang. --Lambiam 15:56, 27 October 2024 (UTC)[reply]

1934–35 North American drought

The article on the 1934–35 North American drought appears to be erroneously dated. I only noticed this because I've been writing about Georgia O'Keeffe, who became widely known for collecting bones in the desert of New Mexico from late 1929 and into the 1930s. These bones are from wild horses and cows that died due to a drought. So when I discovered that this drought was described by Wikipedia as taking place in 1934, I could see something was wrong. Other sources indicate that the media of the time widely reported the drought in the general area as beginning in 1929, not 1934. Can anyone figure out why there is this discrepancy? I did make a comment on the talk page indicating one possible reason. Viriditas (talk) 21:21, 27 October 2024 (UTC)[reply]

The infamous Dust Bowl seems to cover a wider time period. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:54, 27 October 2024 (UTC)[reply]

Understood, but I'm wondering if our article on the 1934–35 North American drought should be widened in terms of the date range. Viriditas (talk) 21:59, 27 October 2024 (UTC)[reply]

The article is poorly written. If anything it should be just 1934 North American drought. The evidence is from tree rings which are incontrovertible, and the extent of the drought can be viewed in the North American Drought Atlas here. Abductive (reasoning) 10:42, 28 October 2024 (UTC)[reply]

It's very unlikely that this was the first and only drought in New Mexico – see Droughts in the United States#Events. In any case, cattle and horses in the wild die for other reasons than drought, and in a dry environment are slow to decay. The bones collected by O'Keefe could have been decades or even centuries old. {The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 12:49, 28 October 2024 (UTC)[reply]

It's important recognize that this drought was for nearly the whole of North America. Abductive (reasoning) 06:06, 29 October 2024 (UTC)[reply]

Yes, this 1934(–5?) drought was, but Viridas assumed that it was the same drought that was responsible for bones collected by Georgia O'Keefe in New Mexico from 1929 onwards, which is clearly unwarrented for the two reasons I have pointed out, over and above the date discrepancy. {The poster formerly known as 87.81.230.195} 94.6.86.81 (talk) 19:20, 29 October 2024 (UTC)[reply]

This is about Alberta, Canada, rather than New Mexico, but:

"Although the early years of the 19th century [presumably 20th century was intended] were wetter, drought returned [to the prairies] during the years of 1910, 1914, 1917, 1918 and 1919, and the drought between 1917-1926 was considered to be especially bad... The global stock market collapsed in 1929 and marked the beginning of the Great Depression. To make matters worse, a severe drought began in the prairies in 1929". [1]

Alansplodge (talk) 12:50, 28 October 2024 (UTC)[reply]